I have MP 5.1, 2x3.33 cpu, 64GB RAM, SSD's and recently added RX 580 Pulse, OS 10.13.6.
I have also found out that Izotope Insight is giving me A LOT of -9173. It is version 1.05c. I just reinstalled it today and during installation I got that OS error that this software is not optimised for my system, looks like 32 bit app!
So I can conform that even if you put 580, you might still get those errors. But as I also use old Apple cinema display 20", I read here somewhere that those displays are giving troubles!? I will try tomorrow to swap that monitor with another one and see if that helps. I am using 4 displays and all other three are full HD resolutions.
I would love to hear about some other metering plug in that will work in 7.1 or more without errors.

I spent a pretty penny on insight 2 and a few others. However most studios, networks use insight and from a lot of blogs here and else where it seems to be the most accurate. Especially to meet various specs for everyone. I was using the waves WLM. But insight is more intuitive. I don't think its 32bit since it came out recently and there are no computers that I know of made for 32 bit, well at least not macs in the last 6 years or so

The RX 580 8GB is arriving tomorrow so will install that and then run insight and see. Since as of now, every time it's on the screen in 5.1 format only showing the levels, I get the -9173

If the GPU card does not address it, then I have no choice to upgrade to a 3.46 and mine as well re-do all of my ram to 6 x 8GB 1333Ghz too.